The present invention relates to a steering system for a motor vehicle.
The steering system has a reduction gear train for transmitting the rotation of a steering wheel to front wheels of the vehicle. It is preferable to vary the gearing ratio in such a manner that it has a small value on either side of the straight-ahead position of the steering wheel and increases as the steering angle of the steering wheel increases. Such a steering system is called a variable ratio steering system and is disclosed various publications, for example U.S. Pat. No. 3,267,763 and Japanese Utility Model Laid Open No. 59-16269.
In the variable ratio steering system, the ratio can not be changed to other ratios than the set values. However, it is desirable for the ratio to be changed in accordance with driving conditions such as vehicle speed, side force exerted on the vehicle and other conditions.